This invention relates to the treatment of head lice and more particularly to saponin containing products that kill human head lice, pediculus humanus capitus, nits (lice eggs) and other types of lice, for example clothing lice, pediculus humanus humanus and other aphids.
Head lice (pediculus humanus capitus) are tiny, wingless, flat bodied parasites that live on the human body and feed by sucking blood from the host. If not destroyed, they multiply rapidly and can spread disease. Head lice are found in both the developed and undeveloped countries of the world and they can be caught by anyone, regardless of race or socioeconomic background. Head lice are generally found on the scalp and cause itchy, red spots. They leave nits or eggs which female lice attach to the base of hair shafts near the scalp. If a lice infestation is present, it is usually indicated by the presence of small, whitish flecks, securely attached to the base of the hair, especially behind the ears and on the forehead. The eggs have a gestation period on the order of one week and infestations are common in day care centers and schools as head lice usually spread by direct contact, which occurs more frequently among children.
Eradication of head lice consists of over-the-counter and prescription medications. Treatment typically involves scrubbing the infested area to loosen the lice followed by application of medication, usually a shampoo which is left on for a prescribed time. After the prescribed time has elapsed, the shampoo is rinsed off. Then, the hair is combed to remove lice. As lice have a gestation period of one week, a second application is done at that time to kill the newly hatched lice as most currently available products to not kill nits.
In view of the foregoing, it will be seen that head lice is a significant public health problem with an eye towards eradication, a number of treatment approaches have developed, namely, pyrethrins, synthetic pyrethrouds (permethrin and bioallethrin), organophosphates (Malathion or maldison), and herbal. All of the foregoing approaches have inherent drawbacks and deficiencies.
Generally, all head lice products contain insecticides and most work by attacking the nervous system of the lice and the active ingredient must have low acute toxicities for humans. Natural pyrethrins are used as pediculicdies worldwide and demonstrate a good safety level. However, although pyrethrins are the most common ingredients in anti-lice products, most of these compositions are shampoos which, due to their presentation, show minimal activity against louse eggs. Shampoos normally fail for several reasons, but most significant among these is the large dilution factor which occurs during use. Depending on how oily the hair to be treated is, the average head of hair will take between 90-150 mls of water to be throughly wetted. Even in hard water areas approximately 5 ml of shampoo is required to work up a good lather, yielding a dilution of 1:30. If the water is soft, the dilution factor could be higher than 1-150.
Many commonly used pediculicidal compositions rely on residual action on the hair by the pesticide after application of the composition to the patient. Permethrin creme rinses are applied after shampooing and rely on the residual action of the insecticide on the hair after the shampoo treatment. One of the drawbacks of Permethrin is that as residual activity wears off, there will be a point beyond which any lice invading the head will not be killed by lower insecticidal levels. Such conditions may lead to the insecticide resistance.
Turning now to the eggs, an insecticide needs to make its way through a physical system that is designed to keep out a variety of chemical materials and to keep water in. The egg shell has a detachable cap that bears a number of air pores that act effectively to exclude fluids by will allow the passage of gasses, and it is through these pores that the developing embryo breathes. However, it is also through these pores that suitable formulations can penetrate. The problems of penetration are dependent on physical parameters. Generally, the more viscous a fluid, and the greater the surface tension, the less chance of penetration of the pores. However, even alcoholic solutions, which have the advantage of a low wetting angle that should allow fluid to flow into the pores, are not free of problems because they can develop air bubbles that are larger than the pores and that subsequently hinder the penetration to the chrionic membrane of the egg.
Aqueous lotions, creme renses and shampoos have too great a wetting angle for fluid to flow into the pores directly, and will only enter if appropriate excipients are included that will wet and flow more readily than the body of the formulation. Consequently, despite the bubbles of a shampoo""s foam being small enough to enter the pores, they are inhibited in an aqueous medium.
It is accordingly an object of the present invention to provide an improved treatment for eradication of head lice and nits.
It is another object of the present invention to provide an improved treatment for the eradication of head lice and nits which is safe.
It is still another object of the present invention to provide an improved treatment for the eradication of head lice and nits which effective.
It is yet another object of the present invention to provide an improved treatment for the eradication of head lice and nits which can be accomplished with one application.
It is a further object of the present invention to provide an improved treatment for the eradication of head lice and nits which is non-toxic to humans.
It is a still further object of the present invention to provide an improved treatment for the eradication of head lice and nits which is new, and therefore, not subject to resistance.
It is a still further object of the present invention to provide a preventative shampoo which when used after the initial treatment, will prevent re-infestation.
In accordance with the present invention, there is provided a method of eradicating Pediculus humanus capitis in humans comprising the steps of applying to the hair and scalp in need of such treatment, an effective amount of a solution consisting essentially of a saponin containing botanical extract, such as yucca extract, at a concentration of at least 200 ppm, based on total weight of the solution, which, for example is found in yucca juice. Thus, a formulation containing from about 40% to 60% yucca juice is effective. The solution is allowed to remain in contact with the hair and scalp for a preslected period of time. Thereafter, the solution is washed from the hair and scalp.
In one aspect of the invention, the solution takes the form of a leave-in conditioner, such as a mousse and includes a thickener, such as a carbomer. In this case the solution is maintained in contact with the hair and scalp overnight while sleeping and is shampooed out in the morning.
In another aspect of the invention, the solution takes the form of a shampoo and includes a surfactant. This shampoo may be employed to wash the conditioner out of the hair and scalp after use or may be used regularly by itself to prevent re-infestations of pediculus humanus capitus and nits.
In still another aspect of the invention, the solution takes the form of a laundry detergent which kills both pediculus humans capitus and pediculus humanus humanus and their respective nits during washing.